Audio I O headset plug and plug detection circuitry

ABSTRACT

A single prong, multiple signal conducting plug and plug detection circuitry is provided. The plug may be electrically coupled to a stereo headset including a microphone. The plug may include four signal conducting regions arranged in a predetermined order along the length of the prong. Detection circuitry may be operative to determine whether a microphone type of plug (e.g., a four region plug including a microphone region and two audio regions, or a three region plug including microphone region and only one audio region) or a non-microphone type of plug (e.g., stereo plug) is inserted into the jack of an electronic device (e.g., mobile phone). Detection circuitry may also detect user activated functions performed in response to user activation of one or more switches included with the headset. For example, the headset may include a single switch for performing a function with respect to a microphone (e.g., end-call function).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser.No. 13/917,432 filed on Jun. 13, 2013, which is a continuation of U.S.application Ser. No. 13/038,172 filed on Mar. 1, 2011, now issued asU.S. Pat. No. 8,467,828, which is a continuation of U.S. patentapplication Ser. No. 11/650,132, filed Jan. 5, 2007, now issued as U.S.Pat. No. 7,912,501 and entitled “AUDIO IO HEADSET PLUG AND PLUGDETECTION CIRCUITRY” which is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

This relates to portable electronic devices, and more particularly toheadset plugs and plug detection circuitry.

Portable electronic devices may include jacks or sockets for receivingconnector plugs (e.g., stereo plug) for headphones or headsets. Audiosignals may be passed from the jack to the headset through electricalconnections formed between the plug and the jack when the plug isinserted into the jack. Known jacks include single prong monaural andstereo plugs and double prong stereo plugs. A drawback of such plugs isthat they lack the ability to handle additional signals which may beprovided by either the headset or the jack. In addition, the doubleprong plug requires a double prong jack, which may occupy valuable realestate in the media device.

What is needed is a single prong plug capable of handling at least oneadditional signal in addition to one or more audio signals. What is alsoneeded is plug detection circuitry to detect which type of plug isreceived in the jack and to detect user activated functions that may beperformed with a headset connected to the plug.

SUMMARY OF THE INVENTION

A single prong, multiple signal conducting plug is provided. This plugmay be electrically coupled to a stereo headset including a microphone.The plug may include four signal conducting regions arranged in apredetermined order along the length of the prong. As such, this plugmay be referred to as a four region plug. The signal conducting regionsinclude a left audio signal region, a right audio signal region, aground region, and a microphone region, where the ground region islocated between the microphone region and either the left or right audiosignal regions.

Detection circuitry may be operative to determine whether a microphonetype of plug (e.g., a four region plug including a microphone region andtwo audio regions, or a three region plug including a microphone regionand only one audio region) or a non-microphone type of plug (e.g.,stereo plug) is inserted into the jack of the electronic device (e.g.,mobile phone). The detection circuitry may provide a signal thatindicates whether the received plug is a microphone or non-microphonetype. For example, when the plug is received, the signal may indicatethat a microphone type of plug is received. Detection circuitry mayprovide another signal that indicates whether a plug is received by thejack. Both signals may be provided to other circuitry, such as aprocessor, within the electronic device for further processing.

Detection circuitry may also detect user activated functions performedin response to user activation of one or more switches included with theheadset. For example, the headset may include a single switch forperforming a function with respect to a microphone (e.g., end-callfunction). When the user presses the switch, the detection circuitry maydetect the occurrence of a switch activation event and provide a signalindicative of that activation that switch to other circuitry (e.g., aprocessor) located in the device. In other embodiments, the headset mayinclude multiple switches (e.g., two switches). The detection circuitrymay detect which one of the switches is activated and provide a signalindicative of which switch is activated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention, its nature andvarious advantages will become more apparent upon consideration of thefollowing detailed description, taken in conjunction with theaccompanying drawings, in which like reference characters refer to likeparts throughout, and in which:

FIG. 1 shows a simplified block diagram of portable media player inaccordance with an embodiment of the present invention;

FIG. 2 shows an illustrative personal media device capable of receivingtwo different types of plugs in accordance with an embodiment of thepresent invention;

FIG. 3 is a simplified schematic diagram of headset system includingstereo headphones, a microphone, and a four region plug in accordancewith an embodiment of the present invention;

FIG. 4 shows a more detailed yet simplified view of a four region plugire accordance with an embodiment of the present invention;

FIG. 5 shows a schematic diagram of detection circuitry in accordancewith an embodiment of the present invention;

FIG. 6 is an exemplary timing diagram showing the state of the signalsprovided by detection circuitry in accordance with an embodiment of thepresent invention;

FIG. 7 shows another exemplary timing diagram illustrating operation ofdetection circuitry using power management in accordance with anembodiment of the present invention;

FIG. 8 illustrates an exemplary timing diagram when a plug that does nothave a microphone region is inserted into jack 510 in accordance with anembodiment of the present invention;

FIG. 9 Shows a schematic diagram of detection circuitry includingsecondary switch detection circuitry according to an embodiment of thepresent invention;

FIG. 10 shows an exemplary timing diagram;

FIG. 11 shows a schematic diagram of detection circuitry includingalternative secondary switch detection circuitry according to anembodiment of the present invention;

FIG. 12 shows an exemplary timing diagram illustrating assertion ofsignals based on detected current levels using detection circuitryoperating in accordance with an embodiment of the present invention;

FIGS. 13 and 14 show two illustrative examples of dual switchconfigurations that may be implemented with respect to a microphone inaccordance with a embodiments of the present invention;

FIG. 15 is a flowchart illustrating steps that may be implemented bydetection circuitry in accordance with an embodiment of the presentinvention;

FIG. 16 is flowchart showing in more detail how one of the steps of FIG.15 may be implemented in accordance with an embodiment of the presentinvention; and

FIG. 17 is a flowchart of steps that may be taken when one or moreswitch activation events are detected in accordance with an embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a simplified block diagram of illustrative portableelectronic device 100 in accordance with the principles of the presentinvention. Device 100 may include processor 102, storage device 104,user interface 108, display 110, CODEC 112, bus 118, memory 120,communications circuitry 122, and jack 130. Processor 102 can controlthe operation of many functions and other circuitry included in mediaplayer 100. Processor 102 may drive display 110 and may receive userinputs from user interface 108.

Storage device 104 may store media (e.g., music and video files),software (e.g., for implementing functions on device 100, preferenceinformation (e.g., media playback preferences), lifestyle information(e.g., food preferences), exercise information (e.g., informationobtained by exercise monitoring equipment), transaction information(e.g., information such as credit card information), wireless connectioninformation (e.g., information that may enable media device to establisha wireless connection such as a telephone connection), subscriptioninformation (e.g., information that keeps tracks of podcasts ortelevision shows or other media a user subscribes to), telephoneinformation (e.g., telephone numbers), and any other suitable data.Storage device 104 may include one more storage mediums, including forexample, a hard-drive, permanent memory such as ROM, semi-permanentmemory such as RAM, or cache.

Memory 120 may include one or more different types of memory which maybe used for performing device functions. For example, memory 120 mayinclude cache, Flash, ROM, and/or RAM. Memory may be specificallydedicated to storing firmware. For example, memory may be provided forstore firmware for device applications (e.g., operating system, userinterface functions, and processor functions).

Bus 118 may provide a data transfer path for transferring data to, from,or between storage device 104, codec 112, communications circuitry 123,baseband circuitry 124, memory 120, and processor 102.

Coder/decoder (CODEC) 112 may be included to convert digital audiosignals into an analog signal, which may be provided to jack 130. Forexample, CODEC 112 may provide audio signals (e.g., left and right audiosignals to jack 130 to be converted into sound by a headset (not shown).In one embodiment, CODEC 112 may provide the left and right audiosignals as single ended outputs. CODEC 112 may receive one or moresignals from jack 130. For example, jack 130 may receive audio signalsfrom a microphone included with a headset connected to the jack. In oneembodiment, CODEC 112 may receive the microphone audio signals as adifferential monaural input.

Jack 130 may be constructed to receive single prong plugs of apredetermined length and diameter. For example, jack 130 may receivefour region plugs and three region plugs. The plugs may be connected toheadsets that may provide microphone and mono or stereo functionality.If desired, the headsets may include integrated switches, that whenactivated, cause a function to be executed. Examples of headsets thatinclude switches can be found, for example, in commonly assigned EricDaniels et al. U.S. patent application Ser. No. 11/650,001, filed Jan.5, 2007, entitled “Bend Switch for Wired Headset,” and Evans Hankey etal. U.S. patent application Ser. No. 60/879,155, filed Jan. 6, 2007,entitled “Wired Headset with integrated Switch,” both disclosures ofwhich are hereby incorporated by reference herein in their entireties.

In addition, jack 130 may include detection circuitry 132. Variousembodiments of detection circuitry are discussed in more detail below,jack 130 may be electrically coupled to processor 102 to transmitsignals between jack 130 and processor 102. For example, detectioncircuitry 132 may provide a HEADSET DETECT signal and MIC signal toprocessor 102. The MIC signal may indicated the presence of headsethaving a microphone connected to jack 130 and may indicate when amicrophone switch is activated. Processor 102 may interpret the signalsreceived from detection circuitry 132 to determine, for example, whichplug type is connected to jack 130 and whether a microphone switch isactivated. In other embodiments, detection circuitry 132 may providethree or more signals to processor 102. For example, when a headsetincludes two or more switch functions, a signal conducting pathway maybe need for each switch function, where one of the pathways may also beused to indicate to processor 102 whether a four region plug is insertedinto jack 130.

Communications circuitry 122 may be included in a carrier circuitryportion (delimited by dashed lines 125) of device 100. Carrier circuitryportion 125 may be dedicated primarily to processing telephone functionsand other wireless communications (e.g., Wi-Fi or Bluetooth). Forexample, baseband circuitry 124 may handle telephone functions. It isunderstood that the carrier circuitry portion operate independent ofother device components operating in device 100. That is, carriercircuitry may be an independently operating subsystem within device 100that may communicate with other components within device 100.

User interface 108 may allow a user to interact with the device 100. Forexample, the user input device 108 can take a variety of forms, such asa button, keypad, dial, a click wheel, or a touch screen. Communicationscircuitry 1122 may include circuitry for wireless communication (e.g.,short-range and/or long range communication). For example, the wirelesscommunication circuitry may be wi-fi enabling circuitry that permitswireless communication according to one of the 802.11 standards or aprivate network. Other wireless network protocols standards could alsobe used, either in alternative to the identified protocols or inaddition to the identified protocol. Another network standard may beBluetooth.

Communications circuitry 122 may also include circuitry that enablesdevice 100 to be electrically coupled to another device (e.g., acomputer or an accessory device) and communicate with that other device.As indicated above, communications circuitry 122 may also includebaseband circuitry for performing relatively long-range communications(e.g., telephone communications). If desired, communications circuitry122 may include circuitry for supporting both relatively long-range andshort-range communications. For example, communications circuitry 122may support telephone, Wi-Fi, and Bluetooth communications.

In one embodiment, device 100 may be a portable computing devicededicated to processing media such as audio and video. For example,device 100 may be a media player (e.g., MP3 player), a game player, aremote controller, a portable communication device, a remote orderinginterface, an audio tour player, a mobile telephone, or other suitablepersonal device. In another embodiment, media player 100 may be aportable device dedicated to providing media processing and telephonefunctionality in single integrated unit. Media player 100 may bebattery-operated and highly portable so as to allow a user to listen tomusic, play games or video, record video or take pictures, place andtake telephone calls, communicate with others, control other devices,and any combination thereof. In addition, device 100 may be sized suchthat it fits relatively easily into a pocket or hand of the user. Bybeing handheld, device 100 is relatively small and easily handled andutilized by its user and thus may be taken practically anywhere the usertravels.

FIG. 2 shows an illustrative portable electronic device 210 capable ofreceiving two different types of plugs. As shown, plug 230 of headsetsystem 220 and plug 250 of headphone system 240 may be inserted intojack 212. Headset system 220 can include stereo headset with amicrophone 224 which is connected to four region plug 230 via wired link224. Stereo headset with a microphone 224 may include left and rightspeakers and a microphone.

Plug 230 may include four signal conducting regions arranged in apredetermined order along the length of a single prong. As shown, plug230 includes, starting from the tip of plug 230, a left audio signalregion 231, a right audio signal region 232, a ground region 233, and amicrophone region 234. The left and right audio signal regions may beinterchanged, however, in this embodiment, ground region is locatedbetween the microphone region and the right audio signal region. Theregions may be separated by insulating rings 235 that electricallyisolate the regions from each other. The electrical connection ofheadset system 220 is discussed below in more detail in connection withFIG. 3 and a more detailed of four region plug is discussed below inconnection with FIG. 4.

Headphone system 240 can include stereo headset 242 which is connectedto plug 250 via wired link 244. Stereo headset 242 may include left andright speakers. Plug 250 includes, starting from the tip, a left audiosignal region 251, a right audio signal region 252, and a ground region253. The location of left and right audio regions 251 and 252 may beswitched. The regions may be isolated from each by insulating rings 255.

FIG. 3 is an illustrative simplified schematic diagram of headset system300 including stereo headphones, a microphone, and a four region plug.FIG. 3 shows how the regions of plug 310 electrically connect to theleft and right acoustic elements 330 and 332 (e.g., speakers), andmicrophone 340. As shown, the left audio signal region, the right audiosignal region, and microphone region can be connected to the positiveterminals of left acoustic element 330, right acoustic element 332, andmicrophone 340, respectively. The ground region can be connected to thenegative terminals of left acoustic element 330, right acoustic element332, and microphone 340, respectively.

Headset system 300 may include a switch 350, for example, to enable auser to activate a function with respect to the microphone. Switch 350may be connected to the microphone and ground regions of plug 310.Switch 350 may be a normally OPEN switch, meaning that in its normalstate, microphone 340 is permitted to transmit signals to the microphoneportion of plug 310. When switch 350 is CLOSED, microphone 340 isshorted.

FIG. 4 shows a more detailed yet illustrative simplified view of a fourregion plug 400. Plug 400 includes four regions, delineated by thenumbers 1-4, separated by insulating rings 405. Plug 400 may be a 3.5 mmplug, where the outer diameter of regions 2-4 is 15 mm. Depending onwhich headset or headphone system plug 400 is connected to, the regionsmay be used for different signal conducting purposes. The tableaccompanying FIG. 4 shows the signal conducting purpose of each regionfor several different systems. For example, for a monaural headset,region 1 may be used for a speaker, regions 2 and 3 may be used asground, and region 4 may be used for a microphone. Note that for theheadset, regions 3 and 4 may be combined to form a single region (notseparated by an insulating ring), thereby providing a three-region plug.Further note that for the monaural headset, regions 2 and 3 may becombined to form a single region, providing a three-region plug with aground region between a microphone region and an audio signal region.Alternatively, in the monaural headset, region 2 may exist but may notconnect to, for example, a speaker in the headset and region three maybe dedicated to ground.

FIG. 5 shows an illustrative schematic diagram of detection circuitry500. Detection circuitry 500 may be operative to determine whether amicrophone type of plug (e.g., a four region plug including a microphoneregion and two audio regions, or a three region plug includingmicrophone region and only one audio region) or a non-microphone type ofplug (e.g., stereo plug) is inserted into the jack of the electronicdevice (e.g., mobile phone). The detection circuitry may provide a MICsignal that indicates whether the received plug is a microphone ornon-microphone type. For example, when the plug is received, a LOW MICsignal may indicate that a microphone type of plug is received.Detection circuitry 500 may also provide a HEADSET DETECT signal thatindicates whether a plug is received by the jack. The MIC and HEADSETDETECT signals may be provided to other circuitry, such as a processor,with the electronic device for further processing by that othercircuitry.

Circuitry 500 includes jack 510 for receiving a plug (e.g., a fourregion plug). Jack 510 includes MIC connector 512, GND connector 513,right connector 514, left connector 515, and headset detect connector516. Connectors 512-515 are staggered such that each connector contactsa different region of a plug inserted into jack 510. For example,assuming plug 230 of FIG. 2 is inserted into jack 510, microphone region234 contacts MIC connector 512, ground region 233 contacts GND connector513, right region 232 contacts right connector 514, and left region 231contacts left connector 515.

Connectors 512-515 may be arranged in a particular order to ensuredesired jack connector to plug regions contacts are made and to ensurethat detection circuitry 500 is able to correctly determine which typeof headset (e.g., headset with or without microphone) is connected tojack 510. The arrangement of connectors 512-515 can match that of a fourregion plug according to the invention. That is, GND connector 513 maybe located between MIC connector 512 and right connector 514. In anotherembodiment, GND connector 513 maybe located between MIC connector 512and left connector 515.

MIC connector 512 may be electrically coupled to CODEC circuitry 520 viabias resistor 527 and transistor 532 (e.g., a FET) via resistor 530. GNDconnector 512 may be connected to a ground source. Right and leftconnectors 514 and 515 may be electrically connected to CODEC circuitry520. In addition, right and left connectors 514 and 515 may beelectrically connected to ground via resistors 522 and 524,respectively. Headset connector 516 may be electrically connected to apower source, called Vdd, via resistors 528 and 529. Vdd may also beconnected to a terminal of transistor 532 via resistor 534.

Left connector 515 and headset detect connector 516 may be selectivelyconnected together by a normally closed switch 518. Switch 518 may beCLOSED when no plug is inserted into jack 510. When CLOSED, Vcc ispulled to ground through resistor 522. Thus, when switch 518 is CLOSED,the HEADSET DETECT signal, which may be provided to a processor (e.g.,processor 102 of FIG. 1), is LOW. A LOW HEADSET DETECT signal mayindicate that no plug is inserted in jack 510. A HIGH HEADSET DETECTsignal may indicate that a plug is inserted in jack 510. The HEADSETDETECT signal may go HIGH when a plug is inserted into jack 510, theplug causes switch 518 to OPEN. When switch 518 is OPEN, headset detectconnector 516 can be pulled up to Vdd.

Detection circuitry 500 may provide a MIC signal, for example, to aprocessor (e.g., processor 102 of FIG. 1). The state of the MIC signalmay indicate whether a headset with a microphone is connected to jack510. In addition, if a microphone headset is connected to jack 510,changes in the state of the MIC signal may indicate the occurrence of aswitch activation (e.g., a user presses a switch to end a telephonecall).

MIC signal may be HIGH when transistor 532 is OFF and LOW whentransistor 532 is ON. Transistor 532 may be an NMOS transistor. CODEC520 may bias the gate of transistor 532 so that it is turned ON when aplug is absent from jack 510 and when a plug including a microphoneregion is inserted into jack 510.

The operation of detection circuitry 500 is now discussed in combinationwith FIG. 6, which is an exemplary timing diagram showing the state ofthe HEADSET DETECT and MIC signals in accordance with an embodiment ofthe present invention. Starting at time t0, when jack 510 is empty, theboth the HEADSET DETECT and MIC signals are LOW, HEADSET DETECT may beLOW because switch 518 is CLOSED, effectively tying connector 516 toground, MIC signal may be low because CODEC circuitry 520 is biasingtransistor 532 to be turned ON pulling MIC signal to ground.

At time t1, when a plug with a microphone region is inserted into jack510, HEADSET DETECT signal goes HIGH and MIC signal may pulse HIGH dueto shorting of wire contacts during plug insertion, but goes LOW. Theprocessor may be configured to ignore any MIC signal until at least apredetermined period of time after HEADSET DETECT goes HIGH to avoiderroneous detection. HEADSET DETECT signal may go HIGH because switch518 OPENS in response to jack 510 receiving a plug. MIC signal maycontinue to stay LOW because transistor 532 is still biased to be turnedON (by CODEC circuitry 520).

Between times t2 and t3, a switch activation event occurs. During thisevent, MIC signal goes HIGH because transistor 532 is turned OFF.Transistor 532 may be turned OFF when MIC connector 512 is shorted toground through resistor 524. For example, MIC connector 512 may beshorted when a switch such as switch 350 of FIG. 3 is CLOSED. Whenshorted, the voltage, including a bias voltage provided by CODEC 520, onconnector 512 drops below a threshold voltage on transistor 532, therebycausing transistor 532 to turn OFF. When transistor 532 is turned OFF,the MIC signal is pulled to Vdd via resistor 534. After time t3, theswitch activation event ends, at which point transistor 532 turns backON, pulling the MIC signal down to ground.

FIG. 7 shows another exemplary timing diagram illustrating operation ofheadset detection circuitry 500 using power management in accordancewith the principles of the present invention. Using power management,CODEC circuitry 520 may provide a bias voltage only when a plug isinserted into jack 510. Starting at time t0 (an empty jack 510), HEADSETDETECT signal is LOW, which may prevent CODEC circuitry 520 fromsupplying a bias voltage, thus providing power savings. MIC signal isHIGH because no bias voltage is provided to turn transistor 532 ON. Attime t1, when a plug with a microphone region is inserted into jack 510,HEADSET DETECT goes HIGH, which may cause CODEC circuitry 520 to providea bias voltage that turns transistor 532 ON pulling MIC signal LOW.Between times t2 and t3, a switch activation event occurs, during whichMIC signal is HIGH. At time t4, the plug is removed, causing HEADSETDETECT signal to go LOW. This causes CODEC circuitry 520 to ceasesupplying a bias voltage and MIC signal goes HIGH.

With respect to FIGS. 6 and 7, a processor may determine whether thetype of plug inserted into jack 510 is a plug having a microphone regionby checking the state of the MIC signal a predetermined time after theHEADSET DETECT signal goes HIGH. In both FIGS. 6 and 7, the MIC signalis LOW a predetermined time (e.g., 10 ms) after HEADSET DETECT goesHIGH, thus indicating that a microphone is present.

FIG. 8 illustrates an exemplary timing diagram when a plug that does nothave a microphone region is inserted into jack 510. Starting at step to,when no plug is inserted into jack 510, both HEADSET DETECT and MIC areLOW. At time t1, when a plug with a MIC region is inserted into jack510, both HEADSET DETECT and MIC go HIGH. MIC may go HIGH because theMIC connector 512 is tied to ground, effectively pulling the gate oftransistor 532 to ground, turning it OFF. MIC connector 512 may becoupled to ground connector 513 a ground region of the plug. Forexample, assuming that plug 250 of FIG. 2 is inserted into jack 510,ground region 255 may electrically couple MIC connector 512 to groundconnector 513.

FIG. 9 shows a schematic diagram of detection circuitry 900 includingsecondary switch detection circuitry 950. Detection circuitry 900 may bethe same as detection circuitry 500, therefore a detailed discussion ofall the components and operation of circuitry 900 is not needed.Secondary switch detection circuitry 950 may be included for detectingswitch activation events of headsets including multiple switches. Forexample, a headset may include two switches, where activation of eachswitch may perform a different function, and where simultaneousactivation of both switches may perform yet another function. FIGS. 13and 14 show two illustrative examples of dual switch configurations thatmay be implemented with respect to a microphone. FIGS. 13 and 14 show anormally dosed switch connected in series with the MIC region of a plug(not shown) and a normally open switch connected in parallel with theMIC region of the plug. The tables accompanying FIGS. 13 and 14 showwhich switch is activated, if any, depending on the open and dosepositions of switches S1 and S2. The table also indicates whether an MICOPEN event (e.g., an event in which the MIC is electrically disconnectedfrom the jack) or MIC SHORT event (e.g., an event in which the MIC isshort circuited to ground. A normal action may occur when switches S1and S2 are in their normal positions.

Referring back to FIG. 9, secondary switch detection circuitry 950 maymonitor a voltage level to determine the occurrence of switch activationevents. Detection circuitry 950 may include voltage detection circuitry952 electrically coupled to node 948. Voltage detection circuitry 952provide a HIGH or LOW signal, labeled MIC ACTION DETECT, depending onthe voltage seen at node 948. In one embodiment, the voltage detectioncircuitry may include a comparator that compares to the voltage at node948 to a reference voltage. The voltage at node 948 may vary amongseveral different voltage levels. For example, node 948 may see a noplug present voltage, a first switch activation voltage, a second switchactivation voltage, a combined first and second switch activationvoltage, and a normal operating voltage. Depending on the voltage seenat node 948, detection circuitry 900 provides the appropriate signalsfor MIC and MIC ACTION DETECT.

FIG. 10 shows an exemplary timing diagram illustrating assertion ofsignals based on detected voltage levels using detection circuitry 900operating in connection with a dual switch, such as those shown in FIGS.13 and 14. FIG. 10 shows the state of the MIC and MIC ACTION DETECTsignals and the voltage detected at node 948, labeled VDETECT. Thedetected voltage may range from an OPEN MIC voltage to a normal voltageto a MIC short circuit voltage. A normal voltage may be detected when aplug with a microphone is inserted into jack 910 and the microphone isoperating in a normal mode (e.g., no switches are being activated), asindicated at time t0. The normal voltage may be the voltage producedwhen the CODEC circuitry biases the microphone and the transistor 932.Between times t1 and t2, a MIC short circuit event occurs. During theMIC short circuit event, MIC signal goes HIGH and VDETECT goes to theMIC short circuit voltage (or ground). Also, during the MIC shortcircuit event, the bias voltage is driven to ground, resulting in anegligible voltage at node 948. Between times t2 and t3, detectioncircuitry 900 returns to normal operation. Between times t3 and t4, aMIC OPEN event occurs. During the MIC OPEN event, VDETECT may go to OPENCIRCUIT voltage, which results in MIC ACTION DETECT going HIGH. Thevoltage at node 948 may be higher during a MIC OPEN event than normaloperation because the microphone is no longer biased by the CODECcircuitry.

FIG. 11 shows a schematic diagram of detection circuitry 1000 includingalternative secondary switch detection circuitry 1050. Detectioncircuitry 1000 may be the same as detection circuitry 500, therefore adetailed discussion of all the components and operation of circuitry1000 is not needed. Secondary switch detection circuitry 1050 mayinclude current detection circuitry 1054 for detecting a current levelflowing through resistor 1052. Depending on the detected current level,circuitry 1050 may provide the appropriate signal (e.g., HIGH or LOWsignal) to MIC ACTION DETECT.

In one embodiment, three different current levels may exist. A firstcurrent level may correspond to a microphone short condition (e.g.,current flow may be high). A second current level may correspond to anormal microphone bias condition (e.g., current flow may be such thatthe microphone is biased). And a third current level may correspond to amicrophone open condition (e.g., current flow may be low and themicrophone is no longer biased). Current detection circuitry 1050 mayassert MIC ACTION DETECT when the third current level is detected. TheMIC signal may be asserted when a microphone short condition exist.

FIG. 12 shows an exemplary timing diagram illustrating assertion ofsignals based on detected current levels using detection circuitry 1100operating in connection with a dual switch, such as those shown in FIGS.13 and 14. FIG. 12 shows the state of the MIC and MIC ACTION DEFECTsignals and the current voltage detected at node 948, labeled DETECTIONCURRENT, DETECTION CURRENT may range from a short circuit current to anormal bias current to an open circuit current. The normal bias currentmay be detected when a microphone electrically connected detectioncircuitry 1100 is operating in a normal mode, as indicated between timest0 and t1. Between times t1 and t2, a MIC short event occurs, which mayresult in MIC signal going HIGH and DETECTION CURRENT going increasingto short circuit current. Between times t3 and t4, a MIC OPEN eventoccurs, which may result in MIC ACTION DETECT going HIGH and DETECTIONCURRENT decreasing to a open circuit current.

It is understood that although FIGS. 9-14 arc discussed in terms orhandling switch activation event executed by two different switches,circuitry may be provided to detect simultaneous activation of twoswitches and additional switches.

FIG. 15 is an illustrative flowchart of various steps that may beimplemented by detection circuitry. Starting at step 1510, one of atleast two types of plugs is received, for example, in a jack of thedetection circuitry. For example, the plug may be a four region plugincluding a microphone region (with a ground region located between themic region and an audio signal region), a three region plug including amicrophone region (with a ground region located between the mic regionand an audio signal region), or a three region plug with no microphoneregion. At step 1520, a HEADSET DETECT signal may be provided (e.g.,asserted) to indicate that a plug has been received. After the HEADSETDETECT signal is asserted, the bias power may be provided to bias, forexample, the MIC DETECT transistor (e.g., transistor 532), if it is notalready being biased.

At step 1530, a determination is made as to which one of the at leasttwo types of plugs is received. This determination may be made apredetermined period of time after the HEADSET DETECT signal has beenasserted to provide sufficient “settling time” before making thedetermination. The determination may be made in one of several differentways, one of which is illustrated in the steps shown in FIG. 16.Referring to FIG. 16, at step 1610, bias power is provided. For example,bias power may be provided by CODEC circuitry. At step 1620, adetermination is made as to whether the plug has a microphone region inthe anticipated microphone region. If yes, the process proceeds to step1630, which provides the bias power to the microphone region. At step1632 the bias power is provided to MIC detect circuitry. If no, theprocess proceeds to step 1640, which provides the bias power to ground.At step 1642, MIC detect circuitry is electrically coupled to ground.

Referring back to FIG. 15, after the determination is made at step 1530,the appropriate MIC signal is provided at step 1540. For example, if amicrophone region is detected, the MIC signal may be LOW, and HIGH ifnot detected. If a microphone region is not detected, then the MICDETECT transistor (e.g., transistor 532) may be turned OFF to savepower. MIC DETECT transistor may be turned by ceasing the supply of thebias power.

FIG. 17 is an illustrative flowchart of various steps that may be takenwhen one or more switch activation events are detected in accordancewith the principles of the present invention. Starting at step 1710, aplug having a microphone region and is electrically connected to atleast one microphone switch is received. For example, the plug may beelectronically connected to a single or dual switch headset. At step1720, the plug may be monitored for a switch activation event. If theheadset has two switches, switch activation event caused by bothswitches may be monitored. For example, one switch may cause an OPEN MICswitch activation event and the other switch may cause a MIC shortcircuit activation event when activated (e.g., pressed by the user). Atstep 1730, a signal is provided in response to a monitored switchactivation event. For example, if a single switch headset is connectedto the detection circuitry and is activated, the MIC signal may beasserted (for at least the duration of the switch activation event).

It is understood that the steps shown in FIGS. 15-17 are merelyillustrative and that steps may be modified, added, or omitted.

Thus it is seen that plug with microphone regions and systems andmethods detecting such plugs and switch activation events are provided.Those skilled in the art will appreciate that the invention can bepracticed by other than the described embodiments, which are presentedfor purposes of illustration rather than of limitation, and theinvention is limited only by the claims which follow.

What is claimed is:
 1. A plug system comprising: a single prong plug ofa predetermined length and diameter including: an audio signal regionhaving a right audio subregion and a left audio subregion, wherein theright audio subregion and the left audio subregion are both audio outputsignal regions; a microphone region; a plurality of insulating regionsto separate the audio signal region from the microphone region; and aground region between the plurality of insulating regions toelectrically isolate the ground region from the microphone region, theleft audio subregion, and the right audio subregion; and a jackincluding a plurality of audio signal connectors electrically coupled tothe audio signal region, wherein the audio signal connectors are coupledto CODEC circuitry used to convert digital audio signals into a leftanalog audio output signal and a right analog audio output signal and tooutput the analog audio output signals.
 2. The plug system of claim 1,wherein the microphone region is electrically coupled to microphonecircuitry.
 3. The plug system of claim 1, wherein the microphone regionis electrically coupled to a microphone switch.
 4. The plug system ofclaim 1, wherein the single prong plug is electrically connected to aheadset comprising microphone circuitry and a plurality of speakers. 5.The plug system of claim 1, wherein the jack is constructed to receive amicrophone type plug or a non-microphone type plug, and wherein theaudio signal connectors are electrically coupled to microphone detectioncircuitry operative to provide a signal indicative of whether thereceived plug is the microphone type plug or the non-microphone typeplug.